Hi personaleu, great suggestion for Google+ Hangouts! I'm sure Google will take it
into account and implement Hangout session video recording > uploading to YouTube very soon. Please note that you've posted suggestion about Google+ in the Google Chat Help forum. Feel free to share it in the Google+ Discuss forum: http://www.google.com/intl/en/+/learnmore/forum/ because this is where you'll have the best chance of receiving an attention to your suggestion.